Various solutions for isolating vibrations are known from the state of art. They usually involve elastomeric materials and in automotive applications vibroisolating devices are employed usually in engine mounts and suspension module top mounts. Their general aim is to ensure low stiffness to efficiently isolate small amplitude vibrations around a certain equilibrium point, while at the same time provide high stiffness for high stroke vibrations to transmit mutual displacements of displaceable objects.
Patent specification U.S. Pat. No. 5,271,595 discloses a resilient support device having a non-linear elastic characteristic, that comprises a body of resilient material provided with two members, coupling the device with a support and a mass to be supported, which are resiliently linked together by two relatively rigid branches, which in turn are connected to each other by at least one resilient crosspiece that is prestressed in traction and is designed to buckle when the forces acting between the coupling members reach a predetermined value, wherein the deformation of the crosspiece(s) is suddenly stopped by an abutment system of relatively high stiffness. The device is applicable as an exhaust pipe support.
Patent specification U.S. Pat. No. 4,984,777 discloses a flexible bearing for supporting a body, such as an internal-combustion engine, that includes a journal bearing that may be attached to a supporting foundation and a support that may be attached to the engine. An elastic spring is connected between the journal bearing and the support while a bearing spring made of a non-creeping material is connected between the journal bearing and the support in parallel with the elastic spring. The bearing spring comprises at least one disk spring having an S-shaped spring constant curve. The disk spring and the elastic spring have load carrying capacities such that, after the weight of the body to be supported is applied to the flexible bearing, the spring rate of the disk spring is essentially zero and the rubber spring is essentially free of elastic tensions.
Other supporting systems are known for example from patent specifications U.S. Pat. No. 5,310,157, DE 3637294 A1, JP 2000-266118, JP 2009-085300 and DE 3608934 A1.
There is an object of the present invention is to provide a vibroisolating device featuring nonlinear force vs. displacement characteristic, substantially symmetrical around a certain and adjustable nonzero displacement value, which might correspond to an equilibrium point of vibrations.
Another object of the present invention is to provide a vibroisolating device which could be employed in a vehicle hydraulic damper, in particular an adjustable active suspension damper, which would effective compensate predefined preload of the damper and would feature relatively high and low stiffness respectively for high and low amplitude vibrations.